Conventionally, for demolishing a very tall smokestack, a crane or a tower crane from the ground is used to build a temporary scaffold from the ground to a top of the smokestack using steel pipes, plate materials, or the like, then workers go up onto the scaffold, and demolish the smokestack by chipping, or demolish a metal smokestack by gas cutting, from an upper end thereof. However, building and demolishing such a temporary scaffold for a tall smokestack requires much labor. Also, the entire temporary scaffold needs to be firmly built, which increases a time for the entire smokestack demolishing work and thus increases cost for the work. Further, since demolishing the temporary scaffold also requires a crane, using the crane in a work period increases cost.
Thus, Patent Literature 1 discloses a smokestack demolishing scaffold apparatus that eliminates the need for building a tall temporary scaffold, and thus eliminates the need for continuously using a crane or a tower crane as described above, and a method for demolishing a smokestack using the scaffold apparatus. FIG. 12 illustrates demolishing of a smokestack using the smokestack demolishing scaffold apparatus. As shown in FIG. 12(a), a smokestack demolishing scaffold apparatus 100 includes, at a circular upper end of an inner cylinder 120 of a smokestack having a double cylinder structure constituted by the inner cylinder 120 and an outer cylinder 122, a scaffold frame 108 including a doughnut-shaped upper floor 102 placed to cover the upper end, and a substantially circular lower floor 106 supported by a column 104 extending downward from the upper floor 102 into the inner cylinder 120 and mounted in the inner cylinder 120. A method for demolishing a smokestack using the smokestack demolishing scaffold apparatus 100 will be described below.
First, as shown in FIG. 12(a), (i) the upper floor 102 is placed on the upper end of the inner cylinder 120 of the smokestack having the double cylinder structure, and the smokestack demolishing scaffold apparatus 100 is locked with the lower floor 106 being mounted in the inner cylinder 120. Then, (ii) one end of a chain 110 having the other end secured to the column 104 is mounted to an inner wall of the inner cylinder 120 to support the scaffold frame 108 on the inner wall of the inner cylinder 120. (iii) In this state, a worker moves onto the upper floor 102 to cut and remove a portion of a predetermined height 122a from the upper end of the outer cylinder 122 (see FIG. 12(a)). (iv) Then, a compact tractor (not shown) having the chain 110 is operated to wind up the chain 110 to slightly raise the scaffold frame 108 so that the upper floor 102 is slightly spaced upward from the upper end of the inner cylinder 120. Then, (v) in that state, as shown in FIG. 12(b), a portion of a predetermined height 120a from the upper end of the inner cylinder 120 is horizontally cut and removed. After the portion of a predetermined height 120a of the inner cylinder 120 is cut, the worker then (vi)) operates the compact tractor to unwind the chain 110 to lower the scaffold frame 108, and as shown in FIG. 12(c), locks the upper floor 102 to a new upper end of the inner cylinder 120. Then, after a mounting position of the other end of the chain 110 to the inner wall of the inner cylinder 120 is changed to a lower position, steps in (iii) to (vi) are repeated. Thus, the worker can successively demolish the smokestack from the upper end thereof while moving down.
Thus, the smokestack demolishing scaffold apparatus 100 eliminates conventional building and demolishing works of a tall temporary scaffold, thereby allowing a tall smokestack to be easily demolished at low cost.